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CURLOPT_HEADERDATA(3) Library Functions Manual CURLOPT_HEADERDATA(3) NAME CURLOPT_HEADERDATA - pointer to pass to header callback SYNOPSIS #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADERDATA, void *pointer); DESCRIPTION Pass a pointer to be used to write the header part of the received data to. If CURLOPT_WRITEFUNCTION(3) or CURLOPT_HEADERFUNCTION(3) is used, pointer is passed in to the respective callback. If neither of those options are set, pointer must be a valid FILE * and it is used by a plain fwrite() to write headers to. If you are using libcurl as a Windows DLL, you MUST use a CUR- LOPT_WRITEFUNCTION(3) or CURLOPT_HEADERFUNCTION(3) if you set this op- tion or you might experience crashes. DEFAULT NULL PROTOCOLS This functionality affects all supported protocols EXAMPLE struct my_info { int shoesize; char *secret; }; static size_t header_callback(char *buffer, size_t size, size_t nitems, void *userdata) { struct my_info *i = userdata; printf("shoe size: %d\n", i->shoesize); /* now this callback can access the my_info struct */ return nitems * size; } int main(void) { CURL *curl = curl_easy_init(); if(curl) { struct my_info my = { 10, "the cookies are in the cupboard" }; curl_easy_setopt(curl, CURLOPT_URL, "https://example.com"); curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, header_callback); /* pass in custom data to the callback */ curl_easy_setopt(curl, CURLOPT_HEADERDATA, &my); curl_easy_perform(curl); } } AVAILABILITY Added in curl 7.10 RETURN VALUE curl_easy_setopt(3) returns a CURLcode indicating success or error. CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3). SEE ALSO CURLOPT_HEADERFUNCTION(3), CURLOPT_WRITEFUNCTION(3), curl_easy_header(3) libcurl 2025-06-03 CURLOPT_HEADERDATA(3)
NAME | SYNOPSIS | DESCRIPTION | DEFAULT | PROTOCOLS | EXAMPLE | AVAILABILITY | RETURN VALUE | SEE ALSO
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